. QST . to thebridge through a variable capacitor. The dummy load must be capable of dissipat-ing nearly the full output from the should be shielded and equipped for coaxial-cable input. The variable capacitor should alsobe enclosed in a metal compartment and shouldbe terminated with coax connectors. A standardT connector and short lengths of coax maybe used for making connection between the trans-mitter, dummy load and variable capacitor. When using this method of power reduction,the bridge is inserted in the transmitter outputline in the usual manner. Then adjust the variablec
. QST . to thebridge through a variable capacitor. The dummy load must be capable of dissipat-ing nearly the full output from the should be shielded and equipped for coaxial-cable input. The variable capacitor should alsobe enclosed in a metal compartment and shouldbe terminated with coax connectors. A standardT connector and short lengths of coax maybe used for making connection between the trans-mitter, dummy load and variable capacitor. When using this method of power reduction,the bridge is inserted in the transmitter outputline in the usual manner. Then adjust the variablecapacitor for normal reflection of the indi-cator and proceed as you would with any otherset of adjustments or measurements. — John W. Stack, W5QQY INPUT CIRCUIT FOR EITHER CRYSTALOR CARBON MICROPHONES THE circuit shown in Fig. 2 permits feeding theoutput of either a crystal or a carbon micro-phone to the speech-amplifier tube. The closed-circuit jacks automatically convert the circuit 1/2 I2AX7. Fig. 2 — Schematic diagram of the speech amplifierdesigned for either crystal- or carbon-microphone input. for whichever type of microphone is used. Whenusing a crystal or other high-impedance niicro-phone, it is plugged into J\. In this application,the cathode circuit for the 12AX7 is completedthrough J2- With Ji closed (microphone plugremoved) and with a carbon microphone pluggedinto Ji, the stage operates as a grounded-gridamplifier. The second half of the dual triode isused as a conventional voltage amplifier with again control in the grid circuit. — Vernon Phillips. W7NPV CUSTOM-MADE NAME PLATES ALL you need to make attractive custom-de--^ signed name plates for the new rig are apackage of transmitter decals (Tekni-Labels,Burbank, Calif.), narrow strips of aluminum,clear finger polish and a piece of crocus cloth orpolishing paper. The strips are cut to the desired width andlength, a mounting hole drilled at each end,polished with the crocus cloth or paper, cleanedof ab
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectradio, bookyear1915
